A duplex reciprocating pump and bellows pump have conventionally been known (see Patent Documents 1 and 2 listed below). These kinds of pumps have a pair of movable partitioning members such as bellows. Moreover, a pair of closed spaces are demarcated into a pump chamber and an actuation chamber by this pair of movable partitioning members.
By alternately introducing an actuation fluid, by means of a switch valve mechanism, into the pair of actuation chambers demarcated in this way, this kind of pump alternately compresses and extends the pump chamber, thereby transferring a transfer fluid. Note that in this kind of pump, generally, a pulsation corresponding to the number of strokes occurs in a discharge flow rate of the transfer fluid.
This pulsation occurs as a result of a pair of suction valves and a pair of discharge valves respectively switching from one pump chamber side to another pump chamber side at an end section of an extension/contraction operation stroke of the bellows, for example. Because such a pulsation causes a variety of difficulties, solutions have been attempted by the duplex reciprocating pumps disclosed in Patent Documents 1 and 2.